I am going to install a led to indicate the current throttle command status, off for stop, slow flashing for mid throttle, and rapid flashing for full throttle. (Phil, I think this is morally acceptable since I have no feedback from a screaming I/C engine, so I am entitled to an optical feedback instead.
The throttle pips are fine, but not very loud coming from inside the box, and I tend to forget the last input. More practise, I know, but still..
I added a few code lines to Mike's sketch, and tested it on an Uno. All seems ok. I am sure you guys could have done it a lot quicker and probably more elegant, but it is ok for me.
If there is an interest, I could share the code here. Pin 4 was still vacant, so I used that for the output to the led. Attaching the entire sketch is probably not useful, since I modified that earlier to use DIP switches instead of jumpers.
The problem that still needs solving is the visibility of the led. For testing, I have used an ordinary 5 mm blue led with a 165 ohm resistor in series (actually two 330 ohm in parallel) supplied directly by the output pin, but I may have to add a booster stage.